1. Field of the Invention
The present invention relates to a transporting device that transports a sheet of paper and is equipped with a function of a positional deflection correction for a sheet of transporting paper, and an image forming apparatus using the same.
2. Description of Related Art
An image forming apparatus equipped with multiple functions, which is simultaneously provided with various functions such as a printer, scanner, a copy machine and a facsimile, has been widely used in recent years. In such an image forming apparatus, a sheet of paper may be deflected to an offset position while the sheet of paper is transported because of mechanical factors or the like in the apparatus. In such a case, the sheet of paper is also deflected from an image forming position thereof. Accordingly, a positional deflection correction for correcting the positional deflection of the sheet of paper has been carried out while the sheet of paper is transported.
In order to correct the positional deflection of the sheet of paper, a pair of conveyor rollers is disposed on a width direction of the sheet of paper so that they are away from each other having a predetermined space therebetween. A pair of deflection detection sensors corresponding to the pair of conveyor rollers is also disposed downstream from the conveyor rollers. The conveyor rollers correct the positional deflection of the sheet of paper by adjusting a speed of each conveyor roller based on the periods of time detected by deflection detection sensors at any two points on the sheet of paper.
In the image forming apparatus, various kinds of sheets of paper having different sizes such as A4 size and B5 size are available therefor. When the sheets of paper to be used have different widths which are very different from each other, only one set of the deflection detection sensors and the conveyor rollers as described above is insufficient for the positional deflection correction of each of the sheets of paper.
In other words, when setting the space between the deflection detection sensors or the conveyor rollers to be narrow corresponding to a sheet of paper having a minimum width, it is difficult to detect the sheet of paper sufficiently and to correct the positional deflection of the sheets of paper sufficiently in a case where a sheet of paper having a maximum width is used. Particularly, if the space between the deflection detection sensors is set to be narrow when using a large sized sheet of paper, the deflection detection sensors perform the detection near the middle of the sheet of large-sized paper so that any sufficient detection accuracy is not obtained.
On the contrary, when setting the space between the deflection detection sensors or the conveyor rollers to be wide corresponding to a sheet of paper having a maximum width, it is difficult to detect the sheet of paper sufficiently and to correct the positional deflection of the sheets of paper sufficiently in a case where a sheet of paper having a minimum width is used.
In order to solve such a problem, for example, Japanese Patent Application Publication No. 2000-335787 or 2007-186291 discloses a transporting device and an image forming device using the same in which plural sets of deflection detection sensors and conveyor rollers are disposed along a width direction of the sheet of paper, the rollers positioned on the position of the deflected sheet of paper are selected based on a width size of the sheet of paper detected by the deflection detection sensors, the sheet of paper is transported with it being held between the selected rollers to correct the positional deflection of the sheet of paper.